In autumn 2024, California’s Monterey Bay skilled an outsized phytoplankton bloom that attracted fish, dolphins, whales, seabirds, and – for just a few weeks in October – scientists. A workforce from NASA’s Ames Analysis Middle in Silicon Valley, with companions on the College of California, Santa Cruz (UCSC), and the Naval Postgraduate Faculty, spent two weeks on the California coast gathering information on the ambiance and the ocean to confirm what satellites see from above. In spring 2025, the workforce returned to assemble information below totally different environmental circumstances.
Scientists name this course of validation.
The PACE mission, which stands for Plankton, Aerosol, Cloud, ocean Ecosystem, was launched in February 2024 and designed to remodel our understanding of ocean and atmospheric environments. Particularly, the satellite tv for pc will give scientists a finely detailed take a look at life close to the ocean floor and the composition and abundance of aerosol particles within the ambiance.
Each time NASA launches a brand new satellite tv for pc, it sends validation science groups around the globe to substantiate that the info from devices in area match what conventional devices can see on the floor. AirSHARP (Airborne aSsessment of Hyperspectral Aerosol optical depth and water-leaving Reflectance Product Efficiency for PACE) is one in all these groups, particularly deployed to validate merchandise from the satellite tv for pc’s Ocean Colour Instrument (OCI).
The OCI spectrometer works by measuring mirrored daylight. As daylight bounces off of the ocean’s floor, it creates particular shades of coloration that researchers use to find out what’s within the water column beneath. To validate the OCI information, analysis groups want to substantiate that measurements immediately on the floor match these from the satellite tv for pc. Additionally they want to grasp how the ambiance is altering the colour of the ocean because the mirrored mild is touring again to the satellite tv for pc.
In October 2024 and Might 2025, the AirSHARP workforce ran simultaneous airborne and seaborne campaigns. Going into the sphere throughout totally different seasons permits the workforce to gather information below totally different environmental circumstances, validating as a lot of the instrument’s vary as attainable.
Over 13 days of flights on a Twin Otter plane, the NASA-led workforce used devices known as 4STAR-B (Spectrometer for sky-scanning solar Monitoring Atmospheric Analysis B), and the C-AIR (Coastal Airborne In-situ Radiometer) to assemble information from the air. On the similar time, companions from UCSC used a bunch of matching devices onboard the analysis vessel R/V Shana Rae to assemble information from the water’s floor.
The Ocean Colour Instrument measures one thing known as water leaving reflectance, which supplies info on the microscopic composition of the water column, together with water molecules, phytoplankton, and particulates like sand, inorganic supplies, and even bubbles. Ocean coloration varies primarily based on how these supplies take up and scatter daylight. That is particularly helpful for figuring out the abundance and varieties of phytoplankton.
The AirSHARP workforce used radiometers with matching expertise – C-AIR from the air and C-OPS (Compact Optical Profiling System) from the water – to assemble water leaving reflectance information.
“The C-AIR instrument is modified from an instrument that goes on analysis vessels and takes measurements of the water’s floor from very shut vary,” mentioned NASA Ames analysis scientist Samuel LeBlanc. “The difficulty there may be that you simply’re very native to 1 space at a time. What our workforce has achieved efficiently is put it on an plane, which allows us to span all the Monterey Bay.”
The bigger PACE validation workforce will examine OCI measurements with observations made by the sensors a lot nearer to the ocean to make sure that they match, and make changes once they don’t.
One issue that may impression OCI information is the presence of artifical and pure aerosols, which work together with daylight because it strikes by means of the ambiance. An aerosol refers to any stable or liquid suspended within the air, reminiscent of smoke from fires, salt from sea spray, particulates from fossil gasoline emissions, desert mud, and pollen.
Think about a 420 mile-long tube, with the PACE satellite tv for pc at one finish and the ocean on the different. Every little thing contained in the tube is what scientists consult with because the atmospheric column, and it is stuffed with tiny particulates that work together with daylight. Scientists quantify this aerosol interplay with a measurement known as aerosol optical depth.
“Throughout AirSHARP, we have been basically measuring, at totally different wavelengths, how mild is modified by the particles current within the ambiance,” mentioned NASA Ames analysis scientist Kristina Pistone. “The aerosol optical depth is a measure of sunshine extinction, or how a lot mild is both scattered away or absorbed by aerosol particulates.”
The workforce measured aerosol optical depth utilizing the 4STAR-B spectrometer, which was engineered at NASA Ames and allows scientists to establish which aerosols are current and the way they work together with daylight.
Flying these devices required use of a Twin Otter aircraft, operated by the Naval Postgraduate Faculty (NPS). The Twin Otter is exclusive for its skill to carry out extraordinarily low-altitude flights, making passes right down to 100 ft above the water in clear circumstances.
“It’s an intense option to fly. At that low peak, the pilots frequently look ahead to and keep away from birds, tall ships, and even wildlife like breaching whales,” mentioned Anthony Bucholtz, director of the Airborne Analysis Facility at NPS.
With the phytoplankton bloom attracting a lot wildlife in a bay already filled with ships, that is no small feat. “The pilots preserve an in depth eye on the radar, and fly by hand,” Bucholtz mentioned, “all whereas following cautious flight plans crisscrossing Monterey Bay and performing tight spirals over the Analysis Vessel Shana Rae.”
Knowledge gathered from the 2024 section of this marketing campaign is on the market on two information archive methods. Knowledge from the 4STAR instrument is on the market within the PACE data archive and information from C-AIR is housed in the SeaBASS data archive.
Different information from the NASA PACE Validation Science Crew is on the market by means of the PACE web site: https://pace.oceansciences.org/pvstdoi.htm#
Samuel LeBlanc and Kristina Pistone are funded by way of the Bay Space Environmental Analysis Institute (BAERI), which is a scientist-founded nonprofit targeted on supporting Earth and area sciences.